Amphibious vehicle power trains

ABSTRACT

An amphibious vehicle power train having an engine ( 2 ) with an output shaft ( 4 ), driving an input member ( 6 ) of a variable speed change transmission ( 11 ). The speed change transmission, which may be a continuously variable transmission is arranged to drive road wheels through an output member ( 8 ). The engine also drives a marine propulsion unit ( 24 ). The axis of the output member ( 8 ) is above the axis of the input member ( 6 ). Four wheel drive may be provided.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/992,037 filed Aug. 12, 2020, which is a continuation of U.S.application Ser. No. 15/707,533 filed Sep. 18, 2017, now U.S. Pat. No.10,744,829, which is a continuation of U.S. application Ser. No.13/907,714 filed May 31, 2013, now U.S. Pat. No. 9,764,611, which is acontinuation of U.S. application Ser. No. 11/793,936 filed Aug. 8, 2008,now U.S. Pat. No. 8,454,398, which is a national phase ofPCT/GB05/05001, filed Dec. 21, 2005, which claims priority from GreatBritain Application No. 0428055.8, filed Dec. 22, 2004, incorporated byreference in its entirety.

BACKGROUND

The present invention relates to amphibious vehicles and in particularto power trains for such vehicles.

In one power train layout for an amphibious vehicle, as described in theapplicant's co-pending application no. GB0422954.8, an engine isarranged so that its crankshaft drives a gearbox from which road andmarine drive outputs are taken. The road drive is turned through anangle of up to 90.degree. by means of a bevel gearbox so as to providean upwardly angled drive to a continuously variable transmission (CVT)speed change unit of the sort having two pulleys interconnected by abelt, which belt runs in a substantially horizontal plane. The output ofthe CVT unit then by means of a further substantially vertical shaftdrives a differential coupled to the rear road wheels.

A problem with the aforesaid arrangement is that the provision of theCVT unit much above the crankshaft axis tends to cause vibration; whilethe location of the CVT unit weighing up to say 30 kg increases theamphibious vehicle's top weight. This in turn raises the vehicle'scentre of gravity and increases its metacentric height, whichdeleteriously affects vehicle handling on both land and water.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an amphibious vehicle powertrain as claimed in claim 1. This improved power train arrangementretains the advantages of the prior arrangement in packaging terms, withreduced vibration and improved weight distribution. Where retractablewheels are provided, it is desirable for such wheels to be clear ofwater when the vehicle banks into turns on water. The geometry of wheelretraction may force the differential(s) to be mounted well above thebottom of the hull; particularly where a deep vee hull is provided tooptimize vehicle handling on water. The power train claimed allows theroad drive to leave the speed change transmission at a level above theengine output shaft, which in turn allows the mass of the engine to bekept low in the vehicle. This keeps the centre of gravity low, andmaximizes metacentric height. These effects minimize vehicle roll andmaximize stability on both land and water.

Where the marine drive is level with the engine output shaft, thisensures a substantially straight run from the engine output shaft to themarine drive. Prior art marine drives such as Aquastrada (U.S. Pat. No.5,562,066) and Simpson (GB 2,134,857) comprise angled drives to themarine drive, which can waste power and create vibration and durabilityproblems.

It should be noted that wherever a speed change transmission is referredto hereinafter in this specification, this is a variable speedtransmission offering a plurality of ratios of input member speed tooutput member speed.

Reference will now be made to embodiments of the invention illustratedin the accompanying drawings, by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side elevation of a power train for an amphibiousvehicle;

FIG. 2 is a schematic side elevation of a power train for an amphibiousvehicle incorporating a reduction gearbox on the engine output shaft;

FIG. 3 is a schematic side elevation of an alternative configuration ofpower train for an amphibious vehicle; and

FIG. 4 is a schematic plan elevation of the alternative version of thepower train as illustrated in FIG. 3 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 , engine 2 supplies drive via output shaft 4.Continuously Variable Transmission (CVT) input member 6 is mounted onthe end of the engine output shaft 4, and connected to a CVT outputmember 8 via drive belt 10. The CVT output member 8 is provided with aCVT output shaft 12, which drives a bevel gearbox 14 driving down to adifferential 20 with a vertical input 18. The CVT input and outputmembers 6, 8 and drive belt 10 form a speed change transmission 11.

The marine propulsion unit 24 receives drive via marine driveshaft 22.

FIG. 2 illustrates the power drive of FIG. 1 with a reduction gearbox 26provided on engine output shaft 4. This figure also shows afour-wheel-drive system, with drive taken forward from CVT output member8 through driveshaft 32 to a forward bevel gearbox 34, which in turndrives front wheels (not shown) through differential 40 with verticalinput 38.

FIG. 3 shows an alternative embodiment of the power train, with thedifferential 20 placed at the back of the CVT output shaft 12, withdriveshafts 27 driving down to wheel driveshafts 28 by chains or belts30.

FIG. 4 is a schematic plan elevation of the alternative version of thepower train as illustrated in FIG. 3 .

Although a longitudinally mounted “North-South” engine is shown, thetransmission layout may in a further embodiment be used with atransverse engine; or even with a vertical crankshaft engine, as isknown in marine prior art. Although an engine output shaft separate toan engine crankshaft is shown, said output shaft may be the enginecrankshaft; or the prime rotating shaft of an electric motor.

The transmission output shaft 12, as shown in FIG. 1 , is above thelevel of the top of the engine; broadly a prime mover; or at least aboveall rotating parts thereof. The transmission output shaft may bedirectly above the input shaft, which is the engine output shaft 4, toallow a forward drive shaft 32 to pass above the engine. In a furtherembodiment, the output shaft may be laterally offset relative to theinput shaft, enabling a lower centre of gravity by running the forwarddrive shaft alongside at least some parts of the prime mover. In anotherembodiment, a centre differential is connected to the forward driveshaft32, to enable speed difference and torque division between front andrear axles.

The marine, propulsion unit 24 is shown diagrammatically, since it maycomprise one or more jet drives. The reduction gearbox 26 is shown asbeing between the engine and both road and marine drives; but in anotherembodiment (not shown), it is connected only to the marine drive. In afurther embodiment (not shown), the reduction gearbox is connected onlyto the road drive. Depending on the characteristics of the prime moverchosen, a speed increase gearbox may be used instead; or even a rangechange gearbox, particularly where all road wheels are driven. Where aCVT is used without a reverse gear, a separate reversing drive may besupplied, as shown in the applicant's co-pending application no.GB0422954.8 (item 110, FIG. 6 ). Clutches or decouplers may be fitted tothe road or marine drive, or to both.

As the power train layout described is essentially tall and narrow, itis particularly suited to a vehicle with passenger seating (not shown)arranged above the power train; more particularly, in line astern. It isalso particularly suited to a vehicle whose road wheels are retractableabove the vehicle water line to reduce hydrodynamic drag when thevehicle is used on water. The wheel retraction may be at an angle to theroad going position, as shown in the applicant's co-pending applicationno. GB0422954.8 (FIG. 1 ).

The seating and wheel retraction arrangements described above areparticularly suited to a planing vehicle; and especially to a planingvehicle with a deep vee hull.

It will be appreciated that various changes may be made to the abovedescribed embodiment without departing from the fundamental inventiveconcept. For example, the speed change transmission unit may be aconventional manual gearbox; a semi-automated manual gearbox; or a fullyautomatic transmission with torque converter and hydraulic drive, as iswell known in road vehicles. The term engine may mean an internalcombustion engine, but the transmission layout described could be foundequally suitable to an external combustion engine, or indeed to a fuelcell and motor combination.

1.-13. (canceled)
 14. An amphibious vehicle power train for anamphibious vehicle having one or more retractable wheels, the amphibiousvehicle power train comprising an engine having an engine output shaftarranged to drive a marine propulsion unit, a variable speed changetransmission and road wheels, the speed change transmission having aninput member and a first output member arranged to interact with theinput member, the first output member having an output axis at a higherlevel than the input axis of the input member, the road wheels beingarranged to be driven by the first output member.
 15. An amphibiousvehicle power train as claimed in claim 14 wherein the axis of firstoutput member is substantially parallel to the axis of the input memberand to an axis of the engine output shaft.
 16. An amphibious vehiclepower train as claimed in claim 14 wherein the speed change transmissionhas a further output member which is arranged to drive the marinepropulsion unit.
 17. An amphibious vehicle power train as claimed claim16, wherein the further output member has an axis at a level below theaxis of the first output member.
 18. An amphibious vehicle power trainas claimed in claim 14 wherein the speed change transmission is mountedsuch that the axes of the input member and the first output member areat a level above the engine output shaft.
 19. An amphibious vehiclepower train as claimed in claim 14 wherein the speed change transmissionis a continuously variable transmission in which the interaction betweeninput and first output members is provided by means of a belt.
 20. Anamphibious vehicle power train as claimed in claim 14 wherein the inputand first output members have conical driving and driven surfacesrespectively.
 21. An amphibious vehicle power train as claimed in claim14 wherein a speed reduction gearbox is provided between the engine andthe speed change transmission or on the engine output shaft.
 22. Anamphibious vehicle power train as claimed in claim 14 wherein the speedchange transmission offers a plurality of ratios of input member speedto output member speed.